Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 2,546	$ 2,850	$ 2,293	$ 2,731
Other comprehensive loss before reclassifications	(190)	(14)	(318)
Amounts reclassified from accumulated other comprehensive loss	4	1	6
Total other comprehensive loss	(186)	(13)	(312)	(25)
Balance at end of period	33,760	2,661	33,760	2,661
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2017-12
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative-effect adjustment of ASU adoption					$ 3
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2018-02
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative-effect adjustment of ASU adoption					(3)
Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(144)	(20)	(16)	(14)
Other comprehensive loss before reclassifications	(4)	(6)	(134)
Amounts reclassified from accumulated other comprehensive loss	4	1	6
Total other comprehensive loss	0	(5)	(128)	(11)
Balance at end of period	(144)	(25)	(144)	(25)
Cash Flow Hedges | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2017-12
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative-effect adjustment of ASU adoption					3
Cash Flow Hedges | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2018-02
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative-effect adjustment of ASU adoption					(3)
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(47)	(44)	(49)	(38)
Other comprehensive loss before reclassifications	(186)	(8)	(184)
Amounts reclassified from accumulated other comprehensive loss	0	0	0
Total other comprehensive loss	(186)	(8)	(184)	(14)
Balance at end of period	(233)	(52)	(233)	(52)
Foreign Currency Translation | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2017-12
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative-effect adjustment of ASU adoption					0
Foreign Currency Translation | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2018-02
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative-effect adjustment of ASU adoption					0
Other
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(2)	(2)	(2)	(2)
Other comprehensive loss before reclassifications	0	0	0
Amounts reclassified from accumulated other comprehensive loss	0	0	0
Total other comprehensive loss	0	0	0	0
Balance at end of period	(2)	(2)	(2)	(2)
Other | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2017-12
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative-effect adjustment of ASU adoption					0
Other | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2018-02
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative-effect adjustment of ASU adoption					$ 0
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(193)	(66)	(67)	(54)
Balance at end of period	$ (379)	$ (79)	$ (379)	$ (79)